1. Technical Field
The invention relates to directional loud speaker systems and more particularly to a acoustic source for delivering intense sound energy to a location spaced a substantial distance from the source.
2. Description of the Problem
A wide variety of acoustic transducers capable of absorbing substantial input energies to produce intense sound fields are available. Directional control of the sound produced and limiting the attenuation of sound field intensity may be effected using a number of types of enclosures and horns and careful positional arrangement of the transducers with respect to one another. The application of the sound system guides selection and blending of these techniques. Some systems, for example those intended for music, should minimize distortion. Many music amplification systems will limit themselves to use of an enclosure and a baffle around the transducers. A public address system tolerates some distortion, particularly at higher frequencies. This favors the use of a high degree of directional control to reduce the rate of drop off in sound pressure with increasing distance from the source. In a public address system it is common for the transducer to be horn loaded.
Of particular interest here is the possibility that a sound system can be adapted for use in the management of crowds or of individuals. It is well known that sound can be intensive enough to be disabling without threatening permanent injury. Were it possible to deliver a sound field of sufficient intensity to disable a person at a distance, or force his retreat, direct physical interaction between those charged with control of crowds, or limiting access to a facility, would be made easier. Such control would also appear far less dramatic and provocative to onlookers and those seeing recordings of the events on television.
Naturally it would of advantage to make such a system mobile. This factor dictates that the system be highly efficient and that sound generated by the system have a minimal drop off in intensity with distance. The directional control of the sound should also be high. The ability to optimize the sound field for the range to a target would also be of advantage.